Slow LAN Performance - Switch Related?

Posted on 2006-06-06
Medium Priority
Last Modified: 2008-02-01
I have a client with about 40 users 6 servers. The current switch layout can be seen at http://www.xtsix.com/CiscoSwitch.htm.

This does not seem to be the most efficient layout to me, but I'm not sure. I am open to any and all recommendations.

They are experiencing slow file access and the Great Plains users in particular complain about perfomance issues.

Aside from physical layout, what else should I look at before making recommendations?

Question by:jra102
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Expert Comment

by:Keith Alabaster
ID: 16845960
Obviously a shame that you cannot use the Gigastack capabilities as this would make a significant difference to peroformance, internally at least.

Are all ports set to 100Mb full duplex?
Are all the attached devices in the same subnet/broadcastt domain or have you vlanned the switches at all?

Author Comment

ID: 16846031
I will double check, but to the best of my knowledge the answer to both questions is Yes.

All ports are set to 100MB FULL and they are all on the same subnet.
LVL 23

Assisted Solution

TheCleaner earned 600 total points
ID: 16846084
Have you ran throughput tests and some basic network tests?  You can get something like Ixia's Qcheck for free to do the throughput tests, or something like this:  http://readerror.gmxhome.de/

Looks like everything is on the same class C, unless that 192.168.1.x is the management VLAN??

I would suggest simple tests first such as plugging into switch 1 and testing performance to the various servers, etc. then move to switch 2 and so on.

You might have a bottleneck based on the interconnects you are doing between switches.  If you have 2-3 more open ports on each switch left you could consider trunking them together (Cisco uses Etherchannel, right?).  That would open the "pipe" between switches.
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LVL 57

Expert Comment

ID: 16848676
TheCleaner:  Correct, Cicso uses Etherchannel.

jra102: You stated that the Great Plains users are complaing.  You doc shows that this server has two connects to two differn switches.  Are the NIC's setup for NIC teaming?  If not, how do you get traffic split accros the NIC's?  

Have you anything that will show you port utilziation?  The 2950 is SNMP enabled, so you could use something like MRTG to look at port utilziation's to see if lack of bandwidth could be an issue.  You will need to verify what the devices connect to the switchports with, especially duplex.  It is not abnormal to have duplex mis-match.  We have a device that has been negotiating 10-half for years, I was originally told that 10-half was all it could do.  Well, we just found out that it can do 100-full.

If switch to switch traffic is getting bottle necked at 100 Full, then follow TheCleaner's advice and setup a Etherchannel connection between the switches.  Cisco supports up to 4 ports in channel, so you could do up to 400 Mbps full duplex.

Expert Comment

ID: 16852036
I havn't got the chance to use cisco switchesyet , but once i had the same problem with 3Com switches, All the ports were conigured on 100 FD. After that i found out that changing it to Auto Neotiation quads the performance, the NIC's work much better when auto negotation is set.

Author Comment

ID: 16852164
giltjr: I don't know if the NICs are set up for teaming...I am just getting acquainted with this environment and will be on site tomorrow, so I will check futher. I will also verify that devices are connecting at 100-full.

What do you think about tomerlei's comment? I have heard different opinions about autonegotiation...I can see setting the workstation ports to auto but should the servers and network devices be forced to 100-full?

Expert Comment

ID: 16852332
My servers are on autonegotiation too, between network devices if both are set on autonegotiation there should be no problem.
As far as i know its the optimal configuration for speed, atleast with 3Com and Nortell switches i got to use so far.
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Accepted Solution

giltjr earned 900 total points
ID: 16853401
I have had and heard of to many issues with autonegotiation.  We only auto desktops, servers are hard coded on the server side and the switch side.  I have seen issues like tomerlei mentioned, one side is hard coded and the other side is auto and the auto side does not auto to well in some cased.  

Part of the problem with auto is there were no standards as to what to default to if you could not agree or detect.  Some manufactures defaulted to half as they felt this would be most common, other defaulted to full as they wanted to default to what would get the best performace.  

With gigabit Ethernet, there was a standard set, so anything that is gig enabled you should be safe with auto.

What you could do is let things default to auto, check what they actually connect at, you must check both the device and switch side.  If they connect at what you want, leave it.  If they do not, then you will should set both sides to what you want.

If the NICs are not setup for teaming, the most likely only one of the NICs is getting used.  If you have users on the "other switch", they may be the one complaining as they must go through a shared uplink then to the server.

In fact you need to check the status of NIC teaming for all servers that are connected to two switches.

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